This invention relates to testing the leaky or non-leaky condition of a flexible, closed container.
It is known to test for leaks in a flexible package (for example a sealed potato chip bag) by resting a weight on the package and measuring the resulting thickness of the compressed package, then repeating the measurement, and finally comparing the two measures of thickness as an indication of the leakage of air from the package. (Franklin, U.S. Pat. No. 4,649,740).
In another technique, the hermetic seal of a food packet is tested by compressing the packet for a period of time between two moving pressure members. A leak is detected if the "pair of members have moved towards one another by more than a predetermined amount by the [end of the] time [period]" (Edmondson, U. S. Pat. No. 4,510,730, col. 1, 1.42). Flexible packages may also be tested for leaks by applying a fluid pressure driven ram at a fixed reaction pressure and detecting "movement of the ram beyond a pre-set limit point . . . as an indication of pressure leak in the package . . . " (Feigel, U.S. Pat. No. 3,918,293, Abstract).
Yet another approach measures how far a package expands in one direction when compressed in another direction (Cassidy, U.S. Pat. No. 4,024,956).
It is also known to test the vacuum integrity of a container having a snap action diaphragm by detecting the speed of inward motion of the diaphragm after it has been pulled to an outward position (Egie, U.S. Pat. No. 4,188,819).